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In my MacBook's networking proxy settings I have "169.254/16" among the list of domains for which to bypass proxy settings:

What purpose does this serve and why do I need it? Can I get rid of it?

  • The 169.254/16 is only for your local network (computers connected to each other locally and not over internet), thus the Proxy is not used for that. – Ruskes Sep 2 '14 at 17:51
  • @Buscar웃: Does it in any way expose me to devices with (perhaps maliciously) self-assigned IPs that happen to be on my network? – orome Sep 2 '14 at 18:02
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    Your local network is not associated with the internet. So no, no danger there. Again, you wont be needing nor using a proxy server for internal communication. The self assigned IP is typical for devices that do not have Internet connection on that network. In that case the IP is used to identify the device on your Local network. Proxy are only used with external communications to hide your IP identity on the www. However the Proxy server does knows your original IP. The Proxy will always cut your speed to 1/2. – Ruskes Sep 2 '14 at 18:24
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It's on the exclude list because a 169.254/16 address is by definition not external to your network. A proxy server relays your requests to other networks. Proxy servers are much less common today than they used to be, but if you are using one, and you didn't have that exclusion, you could get some very strange results.

If you have the proxy enabled without exclusions, you run the risk of the proxy intercepting a request intended for a device on your network, and trying to relay it to the outside world. The possibility exists that the traffic would never reach its intended target on the local network. So the exclusion is telling the OS not to send traffic that should stay local to a proxy meant for external traffic.

I don't know of any reason why it would compromise your own computer's security either way. You can get rid of it, but I don't any advantage of doing so.

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That address range is reserved for "Self Assigned" addresses.

So for example if your network settings on your device are configured to 'DHCP' but for whatever reason you are not able to get a DHCP address your device will assign itself an IP address in the "169.254/16" range.

It is probably in the exclude list because there would never be a valid result from the VPN. And if there were for some strange reason a valid result from the VPN that would likely be bad data. Best not to delete.

  • Other self-assigned addresses are 10.x.x.x and 192.168.x.x (10/8 and 192.168/16 but those are commonly used by WiFi routers. – Harper - Reinstate Monica Jul 10 '17 at 20:21
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I updated my Mac laptop pc to the latest operating system version - MacOS Mojave, and removed *Local, 169.254/16, and the problem solved.

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    You don't describe what problem you were having, but whatever it was, that wasn't the cause of it. You almost certainly want to put that back. – Marc Wilson Nov 24 '18 at 0:06

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